The invention relates to a circuit arrangement for position and advance or feed control of a hydraulic cylinder according to the preamble of claim 1.
A field of use of the invention is for example the drive of a machine tool carriage with a hydraulic cylinder. The feed of the carriage and the acceleration and speed are to be freely programmable, using for example an NC control for this purpose.
The NC control is supplied with the programmed command variable as desired value and as actual value with the controlled variable determined by a displacement pickup of the carriage or the drive and from these a control deviation is formed which is supplied to an amplifier which serves to drive a proportional valve which controls the fluid paths to and from the hydraulic cylinder. If instead of the usual servovalve a proportional valve is used a considerable saving of costs is achieved. However, the control accuracy achievable with a proportional valve is relatively low.
The invention is therefore based on the problem of further developing a circuit arrangement for forming a control for a hydraulic drive by means of a proportional valve in such a manner that even very small feeds or advance rates such as for example 20 mm/min can be produced, a high positioning accuracy of the drive is achieved and the highest possible load stiffness and dynamics of the control are achieved.